pleting the humus and the nitrogen content has been 

 shown by Shutt, Dominion Chemist, from the following 

 figures* : 



TABLE X. Nitrogen-content of Virgin and Cultivated Soils, Indian 

 Head, Saskatchewan. 



Doneghue of the North Dakota Experiment Station 

 arrived at similar conclusions with the fertile Red River 

 Valley soil, under a system of continuous wheat-growing, 

 as indicated in table XI. 



TABLE XL Composition of Old Wheat Soil in Comparison with 

 Virgin Sod.\ 



Doneghue concludes that, "The black clay soil of the 

 Red River Valley has deteriorated in fertility and crop- 

 producing capacity under a continuous system of single 

 cropping with wheat. Such land on the Experiment 

 Station contains approximately one-fourth to one-third 



* Western Prairie Soils. 



fFrom North Dakota Experimental Station Bulletin 126. 



